The present invention is related to switched reluctance electric machines and in particular to a system and method of controlling switched reluctance machines.
Switched reluctance machines (SRM) are a simple, energy-efficient type of electromagnetic device. In particular, SRM devices do not require the use of windings or magnets in the rotor. Rather, SRMs make use of protuberances (i.e. poles) that are magnetically permeable. The stator coils are selectively energized to attract the nearest rotor pole (i.e., bring the rotor pole into alignment with the energized stator coil). By energizing the field coils in sequence, the rotation of the rotor can be selectively controlled. Torque generated by the SRM is controlled by selectively adjusting the magnitude of the current provided to the stator.
The problem with SRMs, when compared to other types of electromagnetic machines, is the torque provided by SRMs can include significant harmonic pulsations during normal operation with conventional excitation schemes. Prior art approaches to reducing torque pulsations in SRMs include both changes to the mechanical design of the machines as well as sophisticated control schemes used to shape the current profile provided to the stator of the SRM.